HKS 91-00 Infiniti G20 SR20DET Outer Valve Spring Set

High-RPM Outer Valve Springs for SR20DE and SR20DET Step 2 and Step 3 Builds

The HKS 22001-AN002 is a set of 16 outer valve springs engineered for SR20DE and SR20DET cylinder heads running HKS Step 2 or Step 3 camshaft upgrades. As engine RPM rises, the time available for each valve to open and close decreases, requiring progressively stronger spring force to maintain accurate cam profile tracking and prevent valve float. The factory SR20 valve springs are calibrated for stock cam lift and RPM limits; once an aggressive camshaft is installed, the reduced dwell time at each lobe transition can cause the valve to separate from the follower at high RPM, a condition known as valve float that leads to loss of power and potential engine damage. The 22001-AN002 uses high-strength alloy steel with heat treatment and shot-peening for fatigue resistance and low inertia. These springs are intended for use with HKS Step 2 camshafts (rev limit 8,000 RPM) and Step 3 camshafts (rev limit 9,000 RPM) on the SR20DET. They are not compatible with the RNN14 Pulsar GTi-R platform. The 22001-AN002 is a direct fitment replacement using the factory retainers and spring seats on compatible SR20DE and SR20DET cylinder heads.

Key Features

• 16-piece outer valve spring set; covers all intake and exhaust valves on a 16-valve SR20 head
• High-strength alloy steel construction with heat treatment and shot-peening for fatigue resistance and long service life at high RPM
• Required for HKS Step 2 camshaft builds targeting 8,000 RPM rev limits on the SR20DET
• Required for HKS Step 3 camshaft builds targeting 9,000 RPM rev limits must be combined with inner springs (22001-AN003) and lash killer kit for full Step 3 compliance
• Direct fitment using factory spring retainers and seats; no machining or head modification required
• CARB compliant will not trigger a CARB acknowledgment requirement
• Compatible with SR20DE and SR20DET engines not compatible with RNN14 Pulsar GTi-R
• Manufactured in Japan by HKS

This Part Fits

Product Specifications

What Is Included

• 16x HKS 22001-AN002 outer valve springs (full intake and exhaust set for one SR20 cylinder head)

Frequently Asked Questions

Do I need the 22001-AN002 for an HKS Step 1 camshaft on the SR20DET?

No. HKS Step 1 camshafts for the SR20DET do not require upgraded valve springs and are designed to work within the factory spring spec at their rated rev limit. Upgraded springs become necessary starting with the Step 2 profile, which targets an 8,000 RPM rev limit where factory spring pressure is no longer sufficient to maintain valve-to-cam contact at peak lift events.

Does the 22001-AN002 include inner springs for a Step 3 build?

No. This set contains outer springs only. A full Step 3 head system requires both outer springs (22001-AN002) and inner springs (22001-AN003), along with lash killer lifters and a valve spring retainer set. If you are building a Step 3 SR20DET, source the inner spring set separately or consider the complete HKS Step 3 head system kit to ensure all components are matched to the same specification.

Will these springs fit the Infiniti G20 SR20DE without modification?

Yes. The G20 uses the same SR20DE cylinder head architecture as the Nissan Silvia and other compatible SR20 platforms. The 22001-AN002 springs are a direct drop-in on the G20 head using the factory retainers and spring seats. Because the G20 uses the naturally aspirated SR20DE rather than the turbocharged SR20DET, a Step 2 or Step 3 camshaft swap on the G20 is common in motorsport builds, making these springs a typical companion upgrade.

Why are these springs not compatible with the RNN14 Nissan Pulsar GTi-R?

The RNN14 Pulsar GTi-R uses a transversely-mounted SR20DET with a different cylinder head configuration, valve geometry, and spring seat dimensions compared to the longitudinally-mounted SR20DET found in the S-chassis Silvia and 180SX. HKS explicitly excludes the RNN14 from the 22001-AN002 application list. Using incorrect springs on the RNN14 head can result in improper installed height and spring pressure, which may cause engine damage.

Do the 22001-AN002 springs require valve spring retainer replacement?

For Step 2 builds, the factory retainers are generally compatible with these outer springs, but HKS recommends the HKS valve spring retainer set (22999-AN001) for maximum compatibility and safety at elevated RPM. For Step 3 builds, the retainer set is considered required. Confirm your specific build requirements with an HKS dealer or qualified SR20 engine builder before reusing factory retainers at the limits of a Step 3 cam profile.

What is the seat pressure and spring rate of the 22001-AN002?

HKS does not publish the seat pressure or spring rate specifications in standard retail documentation for the 22001-AN002. These springs are engineered to match the load requirements of HKS Step 2 and Step 3 SR20DET cam profiles and are validated through HKS internal dyno and track testing. Contact HKS technical support or an authorized HKS dealer for detailed spring data if needed for a custom valvetrain calculation.

Can these springs be used with non-HKS aftermarket camshafts on the SR20DET?

The 22001-AN002 outer springs are compatible with other high-lift SR20DET camshaft profiles from reputable manufacturers, provided the cam lift, duration, and installed spring height are within the range these springs are designed to support. Always verify seat pressure, open pressure, coil bind clearance, and installed height with your camshaft supplier before combining components from different brands in a performance valvetrain build.

Does HKS warranty cover the 22001-AN002 springs?

HKS provides a manufacturer warranty covering defects in materials and workmanship on these valve springs. Under the Magnuson-Moss Warranty Act, installing aftermarket valve springs cannot void the manufacturer warranty on unrelated vehicle systems. For the engine itself, warranty coverage will be affected by any internal engine modifications, which is standard for performance engine components. Consult your HKS dealer for full warranty terms and procedures.

Are these springs a direct swap during a head gasket job or does the head need to come off?

Valve spring replacement requires either a full head removal or the use of a valve spring compressor tool with the head on the engine and the cylinder pressurized to hold the valves closed. Most professional engine builders perform this work during a head gasket replacement or during a dedicated valvetrain service. The 22001-AN002 springs can be installed with the head on the car using compressed air and the appropriate spring compressor, but head-on installation requires significant experience to avoid dropping valves into the cylinder.